A known machine for coating sheets of paper is described in Swiss Patent Application Ser. No. 6112/79 and includes an applicator roller which provides generally thin paper sheets with a coating on one side thereof as they pass therethrough. Since the sheets tend to adhere to the applicator roller after application of the coating, an air nozzle is provided which produces an air flow directed oppositely of the direction of rotation of the roller and approximately tangentially thereto. This air flow detaches each sheet of paper from the roller for deposition on a conveyor belt to convey the sheet away from the roller.
It has been found that although the air nozzle detaches the sheets from the applicator roller, deposition of the sheets on the conveyor belt is not accomplished completely satisfactorily both with respect to the time therefor and to the manner thereof. While the compressed air flow over the entire width of the sheet does reliably detach the sheet from the roller, air flows and pressure differences occur in a direction transverse of the longitudinal sheet length, and this fact together with the normal air pressure present on the back or bottom of the sheet causes a non-uniform detachment of the sheet and a deflection or sagging thereof. This leads to the so-called ear effect, in which the sheet, when viewed in the transverse direction, is raised considerably at its center and in which the two longitudinal ends are only slightly separated from the applicator roller and therefore project upwardly like ears. The main reason for this effect is that after detachment of the sheet, the air supplied by the air nozzle flows away much more rapidly at the longitudinal ends of the sheet than in the center of the sheet, so that the longitudinal ends of the sheet are deflected to a lesser extent. However, the air striking the center of the sheet must first find space for flowing away and creates this space by causing a greater deflection at the center of the sheet.